Impact of Well Stimulation on Coal Porosity of Malaysian Coals for Coalbed Methane (CBM) Study

Coalbed methane (CBM) is an unconventional gas contained in coalbed reservoir.
The character of this reservoir is fundamentally different to conventional gas plays
because coal is almost pure carbon. Coalbed methane (CBM) wells usually have
higher production rate at the beginning of methane production but over time it
decreases until it reaches unprofitable level. Well stimulation is one way to solve
this problem and this research studies acidizing technique for stimulating coalbed
reservoir since there is lack of research done in acidizing of CBM reservoir. The
main objective of this research is to observe the effect on porosity of Malaysian coals
(still not declared as a CBM producer) before and after being stimulated by different
acids that are sulfuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3).
Several laboratory tests are performed to determine the porosity. The experiment
starts by drying the coal samples in the oven for two hours and the weight for each
sample is noted. Each sample is immersed in different acids with different volumes
at constant temperature. After immersing the coal samples in acids for six hours, the
samples are taken out for weight measurement. The experiment is repeated with
different oven temperatures (500C and 1000C) for drying purposes. Upon completion
of this research, a higher porosity is expected to be seen on Malaysian coal samples
after acidizing job is done. So, it means that different acids have different effects on
coal porosity value.